This invention relates to a halogen incandescent lamp suitable primarily for automotive headlight lamps with reflector envelope, and more particularly to a lamp structure suitable for fixing in sealed beam automotive headlight reflectors.
For automotive headlight reflectors, halogen incandescent lamps are usually used that form a closed unit with the reflector envelope preventing moisture or dust from getting in. One end of the reflector envelope is sealed with an optical lens and the other end is sealed with adhesive material placed into the gaps between the electrical lead wires of the lamp and the holes formed in the bottom portion of the reflector envelope. Prior to sealing, the axis of the lamp has to be optically adjusted to the axis of the reflector envelope. The ends of said lead wires are formed to be standard electric contacts as regards their material thickness and distance from each other as well as shape.
U.S. Pat. No. 4,342,142 describes a headlight reflector in which the electric lead wires of the lamp reach to electric blade contacts through holes formed in a plastic base. The lead wires are soldered to the electric blade contacts. A disadvantage of this solution is the troublesome manufacturing process which is less suitable for automation since the standard blade contacts and the lead wires of the lamp do not form a single part.
Unification of the lead wires of the lamp and the standard blade contacts is described e.g. by U.S. Pat. No. 4,310,772 where the same parts serve as lead wires and standard contacts. This solution simplifies the manufacturing process also by the method of fixing of the lamp envelope which is also accomplished by these parts. Tabs formed from the electric lead wire mechanically fix the lead wires on the pinch sealed portion of the envelope of the lamp. At the same time, a socket disc for the optical adjustment of the incandescent coil of the lamp appears as an additional part.
A solution very similar to the previous one is described in U.S. Pat. No. 4,429,249. This solution requires no separate part for the optical adjustment of the incandescent coil. This adjustment is accomplished directly by fixing the electric lead wires loosely fitted in the holes formed in the bottom portion of the reflector envelope with an adhesive material in an appropriate position. The electric lead wires end in standard connectors which, being knife-shaped contacts, have a flat surface and the planes of their flat surfaces are perpendicular to the pinched portion of the envelope of the lamp. However, this construction is not suitable for connectors where the planes of the knife-shaped contacts are parallel to the pinched portion of the lamp. This construction is also not suitable when one of the connectors raises from the plane placed through the central axis of the lamp at a distance corresponding at least to the radius of the lamp.
Having standard connector contacts and electric lead wires forming one part therewith, H4703 type headlight lamps of General Electric Company have been sold. This type of headlight lamps could be ordered on the basis of GE Lighting, Miniature and Sealed Beam Lamp Catalog, 9/97. In these lamps, the electric lead wires are bent wires with tubular cross-section that are flattened at the places of fixing to the reflector envelope and at the places of the connector contact. The purpose of flattened portions at the place of fixing to the reflector envelope and at the place of the connector contact is providing an adhesion of appropriate strength and forming the standard knife-shaped contact, respectively. However, forming the electric lead wires in this way has several disadvantages. On one part, forming the knife-shaped contacts by flattening is disadvantageous since the tolerances specified by the standard are hard to reach using this method; on the other part, leakage may occur at the place of fixing to the reflector envelope if the flattening is not perfect. It is an additional disadvantage that bending the wire of tubular cross-section on a machine is an operation that is hard to control, and this bending has to be performed on both electric lead wires independently of the placing of the connectors.
Thus there is a particular need for a halogen incandescent lamp in which the electric lead wires make up a construction forming one part with the connector contacts and meeting the tolerance requirements of the standard easily. This part comprises no separate components and is easy to bend. It does not require flattening.
A halogen incandescent lamp for automotive headlight reflectors is provided having at least one incandescent coil and an envelope including a pinched portion from which electrodes project. Clamping saddles made of bent metal strips are mounted on the pinched portion. Each clamping saddle has a wing extending in a plane placed across the central axis of the lamp, and each electrode is electrically connected to a clamping saddle. The lamp comprises lead wires that are cut to shape from metal strips of appropriate thickness and have an elongated shape in the direction of the central axis of the lamp. Each lead wire is mechanically and electrically connected to a wing of a clamping saddle.
This invention has several advantages. The primary advantage is that the connector contacts with a tolerance specified by the standard are easy to manufacture since the starting material is a rolled sheet with tight tolerances and the pressing operation which is more difficult to control in the process is left out. By cutting out from a sheet, any shape can be formed which enables that a connector contact and an electric lead wire are made as one piece. This eliminates the problems that arise when soldering several parts together. Finally it is also a significant advantage that in case of need bending is performed significantly easier and more accurately on a sheet part than on lead wires with circular or tubular cross-section. It is not necessary to perform bending on the electric lead wires in the event of some connector contacts conforming to the standard, while it is necessary to make bending on lead wires with circular or tubular cross-section in every case. In this way, standard connector contacts are made where the planes of said knife-shaped connectors are parallel to the pinched portion of the envelope of the lamp.